This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for Global Effects of a Probiotic Strain on Lactating Women (NCT01124448), a non-randomized na study. The primary outcome is Evidence of Clinically Definite Mastitis Confirmed by Microbiological Cultures and Somatic Cell Counts.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01124448 |
| Phase | NA |
| Condition | Mastitis |
| Allocation | Non-Randomized |
| Design model | Parallel |
| Masking | None (open label) |
| Enrollment | 40 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Universidad Complutense de Madrid |
| Results posted | Yes |
2. Clinical Question
Population
The study enrolled lactating women: 25 with mastitis and 15 without mastitis. The registry describes the mastitis group as women with mastitis and the other group as lactating women without mastitis. It does not report further eligibility criteria, participant characteristics, or how mastitis was diagnosed for enrollment.
Intervention
Women with mastitis received Lactobacillus salivarius PS2, described as 9.5 log per day for 21 days. The study's stated aim was to examine microbiological and other biological effects of probiotic administration in lactating women with mastitis.
Comparator
The comparison group comprised 15 lactating women without mastitis, identified in the arm description as Lactobacillus salivarius PS2B. The registry does not describe this group as a randomized or like-for-like untreated control for women with mastitis. The groups differ in mastitis status, and allocation was non-randomized.
Primary question
The primary outcome was total milk bacterial count at the end of the study, after probiotic administration for 21 days, expressed as log10 CFU/mL. The stated timeframe is one week. The registry's objective was to examine whether probiotic administration had effects that could support a beneficial effect in lactational mastitis, but it does not report the bacterial-count estimates or a comparison result.
3. Trial Design
This completed study is registered as NCT01124448, under the title “Global Effects of a Probiotic Strain on Lactating Women.” Its official title describes oral probiotic administration and microbiological, immunological, transcriptomics, and metabolomics effects. Universidad Complutense de Madrid is listed as sponsor. The registry records the study as non-randomized, with no masking and a parallel model. Its phase is listed as NA.
The total enrollment was 40. The arm descriptions identify 25 women with mastitis who received Lactobacillus salivarius PS2, and 15 lactating women without mastitis in the PS2B group. The intervention description specifies 9.5 log per day for 21 days for the mastitis group. Because allocation was non-randomized and the groups differ in mastitis status, their outcomes would not constitute a like-for-like comparison of treated and untreated women with the same condition. The registry record itself cautions that the arms are not a like-for-like control comparison.
The study is described as multidisciplinary, with its stated aims including microbiological, immunological, genomic, metagenomic, transcriptomic, and metabolomic investigation. Four secondary outcome descriptions concern gene expression in milk somatic cells, urine metabolic profile, milk macronutrient and electrolyte profiles, and milk immunological profile. The record lists five outcome measures in total. It does not describe the methods used to assign participants to the arms, the timing of all measurements, or the detailed analysis plan.
The recorded study start is 2011-03, and primary completion is 2013-09. The status is completed. These design and registry entries describe the study structure; they do not establish the size, direction, or precision of any treatment effect.
4. Participant Flow and Accounting
The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.
Overall Study
| Stage | Lactobacillus Salivarius PS2 | Lactobacillus Salivarius PS2B |
|---|---|---|
| STARTED | 25 | 15 |
| COMPLETED | 23 | 12 |
| NOT COMPLETED | 2 | 3 |
Reasons for not completing this period:
| Reason | Lactobacillus Salivarius PS2 | Lactobacillus Salivarius PS2B |
|---|---|---|
| Lost to Follow-up | 0 | 3 |
| Protocol Violation | 2 | 0 |
5. Baseline Characteristics
The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.
Population: This study was designed to evaluate a high number of microbiological, biochemical or immunological parameters before and after the administration of a probiotic to women with mastitis and to elucidate which of them can be useful as biomarkers in future studies. The number of participants was considered suitable for such purpose.
| Characteristic | Unit | Lactobacillus Salivarius PS2 | Lactobacillus Salivarius PS2B | Total |
|---|---|---|---|---|
| Participants analysed | 25 | 15 | 40 | |
| Age, Continuous | years | 28.2 (SD 7.7) | 29.0 (SD 7.8) | 28.6 (SD 7.7) |
| Sex: Female, Male: Female | Participants | 25 | 15 | 40 |
| Sex: Female, Male: Male | Participants | 0 | 0 | 0 |
| Region of Enrollment: Spain | participants | 25 | 15 | 40 |
| Total milk bacterial count (initial) | log10 CFU/mL | 4.08 (SD 0.20) | 3.19 (SD 0.59) | 3.63 (SD 0.39) |
6. Primary Endpoint
The registry lists the primary outcome as Evidence of Clinically Definite Mastitis Confirmed by Microbiological Cultures and Somatic Cell Counts, measured over one week.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | 95% Confidence Interval |
| Unit | log10 CFU/mL |
| Endpoint classification | Continuous Endpoint |
The primary endpoint is total bacterial count in milk at the end of the study, after probiotic administration for 21 days. It is expressed as log10 CFU/mL, meaning the logarithm of the number of colony-forming units per millilitre of milk. The registry identifies the measure as a mean and states that its dispersion should be represented by a 95% confidence interval. The outcome timeframe is described as one week.
A milk bacterial count is a microbiological measure, rather than a direct report of symptoms or a clinical event. The registry title for the outcome refers to evidence of clinically definite mastitis confirmed by microbiological cultures and somatic cell counts, while the outcome description specifies total milk bacterial count at the end of the study. Those descriptions should be read as the registry's wording; the record does not provide further operational detail on how the measure was derived or how confirmation was defined.
In general, a prespecified primary endpoint gives a study a central outcome for evaluating its main question. A continuous measure such as this can be summarized with a mean, while a confidence interval indicates the uncertainty around an estimate under the analysis assumptions. The registry record does not report the observed mean, its confidence interval, group-level values, or an estimated between-group contrast. The endpoint's numerical result and its precision are therefore not reported in the registry record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record establishes that the primary outcome was total milk bacterial count at the end of the study, measured in log10 CFU/mL. It also identifies the measure as a mean with 95% confidence interval dispersion. However, the record does not report the mean, the interval, or any numerical comparison between groups. There is therefore no posted primary-outcome estimate from which to describe the direction, magnitude, or precision of a difference.
This absence matters especially because the study was non-randomized. The 25 women with mastitis who received Lactobacillus salivarius PS2 were compared in the study design with 15 women without mastitis. The registry cautions that these arms are not a like-for-like control comparison. A difference between such groups, if one were reported, could reflect the difference in mastitis status or other group differences as well as any effect associated with probiotic administration. Without random allocation and a suitably comparable control group, the design would not isolate an intervention effect in the way a randomized comparison aims to do.
The registry describes several biological domains of interest, including gene expression, urine metabolites, milk composition, and milk immunological profile. These objectives provide context for the study's multidisciplinary scope, but the record does not include numerical findings for those outcomes either. The outcome descriptions alone cannot establish that any marker changed, in which direction it changed, or how certain such a change would be.
The record lists zero analyses. It does not provide an analysis population, model specification, adjustment strategy, missing-data method, or multiplicity procedure. Consequently, readers cannot assess how the stated outcome was analyzed, whether the intended analysis was carried out, or whether any reported inference accounts for multiple outcomes. No result should be inferred from the absence of a posted analysis.
In general, a confidence interval conveys the range of values compatible with an estimate under the statistical model and assumptions used; its width is relevant to precision. Since no interval is posted, precision cannot be assessed for the primary endpoint. The registry does not report a p-value or a hypothesis-test result for this outcome.
The record also reports no serious adverse events or other adverse events in either listed arm, with 0 affected among 25 at risk in the mastitis group and 0 affected among 15 at risk in the PS2B group. Death counts are not reported in the registry record. These registry entries are safety reporting figures, not evidence about the primary endpoint or a basis for inferring an overall benefit or harm. Taken together, the posted information describes the question and design, but does not provide the outcome estimates needed to characterize the study's findings.
9. Statistical Methods Explained
Statistical methods explain how observations are converted into estimates and how uncertainty is represented. The registry record identifies a continuous primary measure summarized as a mean, with a 95% confidence interval. It does not report the detailed statistical analysis plan, the methods used for the outcome, or numerical outcome estimates. The concepts below are general explanations, not descriptions of methods confirmed for this study.
What does a mean describe?
General: A mean is a measure of the central level of a continuous variable. It combines individual observations into one summary, which can be useful when the scientific question concerns average bacterial count. A mean does not show the full distribution of observations. The same average can arise from data with different degrees of variation or different shapes, so the summary is most informative when the data distribution and supporting uncertainty are also considered. The registry identifies the primary parameter as a mean but does not report the observed value or the underlying distribution.
What does log10 CFU/mL mean?
The endpoint is expressed as log10 CFU/mL: a logarithmic expression of colony-forming units per millilitre. General: Logarithms represent values on a transformed scale, so a difference on that scale is not interpreted as an ordinary arithmetic difference in the original measurement units. Any interpretation should respect the stated scale and the analysis used. No numerical estimate or contrast is reported in the registry record, so no scale-specific effect can be described for this study.
How should a confidence interval be read?
General: A confidence interval expresses statistical uncertainty around an estimate under the method's assumptions. A narrower interval indicates greater precision than a wider interval, while the interval's location indicates which values are compatible with the estimate under that procedure. It is not a guarantee that the true value falls within the particular interval, and it does not correct for biases in study design or analysis. Here, the registry specifies 95% confidence interval dispersion but gives no interval endpoints. The precision of the primary result is therefore not assessable from the posted record.
Why does the comparison design matter?
General: Random allocation helps balance measured and unmeasured participant characteristics across treatment groups, on average, and supports causal interpretation when the trial is conducted and analyzed appropriately. Non-random allocation can leave groups systematically different before treatment. In this study, the registry identifies one group as women with mastitis who received the probiotic and the other as lactating women without mastitis. It explicitly says the arms are not a like-for-like control comparison. Any observed contrast between these groups would therefore need cautious interpretation, and would not by itself identify the effect of probiotic administration among comparable women with mastitis.
Comparisons within a group over time can also be affected by time trends, changes in measurement, and other events during follow-up. The registry does not provide enough detail to establish whether a within-group analysis was conducted or what approach it used. It reports the primary outcome timeframe as one week and describes measurement at the end of the study after 21 days of probiotic administration. The relation between those timeframe descriptions is not further explained in the registry record.
What is over-dispersion?
General: Over-dispersion occurs when the observed variability is greater than a statistical model assumes. If a model underestimates variability, standard errors and confidence intervals may be too small, which can make results appear more precise than warranted. This issue is relevant to some types of count data, but the primary outcome is described as a mean of log-transformed bacterial counts. The registry does not report whether over-dispersion was assessed or whether a model requiring such an assessment was used.
What can planning calculations tell readers?
The registry describes a planning illustration based on an observed effect, with a two-sided significance level of 0.05, equal allocation between arms, and a normal approximation; the target effect is a stated fraction of the observed effect. Such calculations are planning illustrations, not observed power and not results from the study. The record does not report numerical sample-size outputs, and its actual group sizes were 25 and 15, rather than equal allocation. No conclusion about adequacy of enrollment or power can be drawn from the posted information. The trial's own sample-size justification is not reported in the registry record.
General: Power calculations depend on assumptions about the effect to detect, variability, test procedure, and allocation. If the true effect differs from the assumed effect, the operating characteristics differ too. A calculation based on an observed effect can be especially uncertain because that estimate is itself subject to sampling variation. It should not be interpreted as a measure of the probability that the study's finding is true. No such probability is reported.
Overall, the posted methods information is limited to the primary outcome's form and dispersion, the study allocation structure, and a description of planning assumptions. Detailed estimators, model diagnostics, covariate choices, hypothesis tests, and uncertainty calculations are not reported in the registry record. General statistical concepts can clarify what these methods would mean, but cannot fill in the study's unreported analysis choices or results.
10. Multiplicity, Missing Data and Analysis Populations
The study lists five outcome measures and describes several secondary biological outcomes, including milk somatic-cell gene expression, urine metabolic profile, milk macronutrient and electrolyte profiles, and milk immunological profile. The primary outcome is total milk bacterial count. The registry record does not report how many outcomes were analyzed, which outcomes were formally tested, or whether a hierarchy of outcomes was specified.
General: When investigators examine multiple outcomes or perform multiple tests, the chance of at least one apparently notable finding can increase. A multiplicity strategy may define a primary test, adjust inference across tests, or distinguish confirmatory from exploratory analyses. The registry record does not report a multiplicity procedure, so readers cannot determine whether or how multiple comparisons were addressed.
The record lists zero analyses and does not report an analysis population, participant flow, missing-data counts, or a method for handling missing observations. It is therefore not possible to tell whether the outcome summaries would include all enrolled participants, only participants with measurements, or another defined group. The reasons for missing observations, if any, are not reported in the registry record.
General: Missingness can affect interpretation when the availability of measurements is related to participant characteristics or outcomes. Methods such as complete-case analysis or imputation make different assumptions, and the appropriate approach depends on the data and estimand. No missing-data method or sensitivity analysis is reported for this study. The registry also does not report interim analyses, stopping rules, or a detailed statistical analysis plan. These absences limit assessment of how outcomes and uncertainty were handled; they are not evidence that a particular method was or was not used outside the registry record.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Lactobacillus Salivarius PS2 | 0 | 25 | 0.0% |
| Lactobacillus Salivarius PS2B | 0 | 15 | 0.0% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Lactobacillus Salivarius PS2 | 0 of 25 |
| Lactobacillus Salivarius PS2B | 0 of 15 |
The registry reports no serious adverse events in either listed group: 0 affected among 25 at risk in the Lactobacillus Salivarius PS2 group and 0 affected among 15 at risk in the Lactobacillus Salivarius PS2B group. It also reports 0 other adverse events among 25 at risk and 0 among 15 at risk. These are the figures recorded for the groups; they do not describe the primary bacterial-count outcome.
A zero in an adverse-event entry means that no affected participants are recorded for that category in the registry. It does not establish that an event is impossible or that all potential harms were captured. Interpretation depends on how adverse events were defined, sought, monitored, and reported. Those details are not reported in the registry record. The deaths fields are null, so death counts are not reported in the registry record; a null entry should not be read as a reported count of zero.
The study was non-randomized, and its arms were not a like-for-like control comparison. These safety figures therefore do not support a controlled comparison of event risk between otherwise comparable groups. They are descriptive registry entries and should be read within the limits of the recorded information.
12. What the Result Does, and Does Not, Mean
The registry record describes a completed, non-randomized study of probiotic administration to lactating women with mastitis, alongside a group of lactating women without mastitis. It specifies the primary measure as total milk bacterial count, expressed as log10 CFU/mL, after probiotic administration for 21 days. It also describes a broad set of biological objectives covering microbiological, immunological, gene-expression, and metabolic measures.
The record does not report the primary mean, its 95% confidence interval, or a numerical comparison. It also does not report numerical findings for the secondary outcomes. As a result, the posted information does not establish whether bacterial counts or other measures changed, how large any change was, or how precise an estimate might be. It is not possible to characterize the direction or statistical significance of an outcome from the registry record.
The study design also limits what comparisons could mean. The intervention group had mastitis, whereas the comparison group did not, and allocation was non-randomized. The registry explicitly cautions that the arms are not a like-for-like control comparison. A difference between them, even if reported, could not automatically be attributed to the probiotic rather than to group differences related to mastitis or other factors.
General: A study's scientific aim, its design, and its observed estimates answer different questions. An aim is not evidence that an effect occurred; a design determines which interpretations are supported; and numerical results are needed to assess magnitude and uncertainty. Here, the record gives the aim and some design details, but not outcome estimates or analysis results. The recorded adverse-event counts are descriptive and do not resolve the missing efficacy information or establish a comparative safety effect. The registry's stated hypothesis and intended search for markers should therefore be understood as study aims, not as findings.
13. Why This Trial Matters Statistically
This study is statistically notable for the distinction between an intervention group and a comparison group that is not designed as a like-for-like control. The mastitis group received Lactobacillus salivarius PS2, while the comparison group consisted of lactating women without mastitis. Non-random allocation and differing mastitis status make it important to separate descriptive group comparisons from causal claims about the intervention.
The primary endpoint is a continuous microbiological measure on a logarithmic scale, with a mean and 95% confidence interval specified. That framing highlights the importance of reporting both the estimate and its uncertainty. The registry record gives the intended summary but no numerical estimate or interval, leaving readers unable to judge magnitude, precision, or compatibility with a range of possible effects.
The record's multidisciplinary scope also illustrates a common statistical challenge: a study can examine many kinds of biological outcomes. When multiple outcomes are investigated, clear identification of the primary question and transparent handling of multiplicity help readers distinguish confirmatory evidence from exploratory findings. The registry lists five outcome measures but does not report the analysis details or multiplicity approach.
The study's enrollment was 40, divided into groups of 25 and 15. Those counts describe the participants enrolled, not the number with completed outcome measurements or an adequate basis for a particular statistical conclusion. The registry does not report outcome availability, a sample-size justification, or numerical planning outputs. These omissions underline why enrollment alone cannot establish statistical precision or power.
More broadly, the record shows why registry descriptions and posted results are both needed for appraisal. Design information frames the possible interpretation, while effect estimates, uncertainty, analysis methods, and missing-data details are needed to evaluate findings. The absence of those details limits the statistical conclusions that can be drawn.
14. Limitations
- The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
- Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.
The registry record does not report the primary outcome estimate, its 95% confidence interval, or a between-group analysis. It also provides no numerical results for the secondary outcomes. The completed status therefore does not mean that the registry record contains enough information to assess the study's findings.
The non-randomized design and the different mastitis status of the groups are important limitations for comparative interpretation. The record itself states that the arms are not a like-for-like control comparison. It does not describe how participants were assigned, whether any adjustment for group differences was planned, or which potential confounders were measured.
Enrollment was 40, with 25 participants in the mastitis group and 15 in the group without mastitis. The registry does not report how many participants contributed data to each outcome, whether any participants withdrew, or how missing measurements were handled. It also does not report the study's own sample-size justification, detailed statistical plan, model diagnostics, or multiplicity strategy.
The registry outcome title refers to clinically definite mastitis confirmed by microbiological cultures and somatic cell counts, while its description specifies total milk bacterial count at the end of the study. It does not provide additional operational definitions or explain the relation between the one-week timeframe and the description of measurement after 21 days of administration. Such details are not reported in the registry record and should not be inferred.
Finally, the adverse-event entries list zero affected participants for serious and other adverse events, while deaths are not reported in the registry record. The record does not describe event definitions, ascertainment, or follow-up completeness. These limitations concern what can be learned from the registered information, and do not establish what may or may not have been collected outside it.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Global Effects of a Probiotic Strain on Lactating Women — NCT01124448.
- Registry record last updated 2014-08-20; status last verified 2014-08.
- Results first posted 2014-08-20.
- Data retrieved from ClinicalTrials.gov on 2026-11-09.
- Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.
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18. Record Summary
NCT01124448 is a completed, non-randomized, unmasked, parallel study sponsored by Universidad Complutense de Madrid. The registry records enrollment of 40: 25 women with mastitis who received Lactobacillus salivarius PS2, described as 9.5 log per day for 21 days, and 15 lactating women without mastitis. Its primary outcome is total milk bacterial count in log10 CFU/mL, described as a mean with 95% confidence interval dispersion.
The record lists four secondary outcome descriptions and five outcome measures overall. It cautions that the two arms are not a like-for-like control comparison. No primary or secondary outcome estimates, analysis results, detailed statistical plan, or missing-data approach are reported in the registry record. Serious and other adverse-event entries list zero affected participants in both groups; death counts are not reported in the registry record. Thus, the record describes the study question and structure but does not provide numerical results for assessing outcome magnitude or precision.